Down the Mine is the twenty-fifth episode ever made in Season 1.
One day while Thomas is waiting at the junction, Gordon, who is in disgrace after causing trouble and falling into a ditch, pulls in with some trucks. As soon as Gordon stops, Thomas cracks a joke about ditch water. Before Gordon can respond, Thomas leaves with his coaches.
Annie and Clarabel are shocked at Thomas' behaviour, and scold him for it. Thomas is pleased with his clever joke though and runs off to go to the lead mine. The mine was used a long time ago by miners digging for lead who made tunnels under the ground. While the roofs of the tunnels are strong enough to hold up trucks, they cannot sustain the weight of engines. At the mine, there is a board displaying a clear warning that engines must not pass that point. Thomas considers the board to be silly and would often try to pass it, however his driver prevented him.
That morning however, Thomas had made a plan to get past the board. When Thomas' fireman leaves the cab to change the points, Thomas bumps the trucks fiercely and knocks his driver off the footplate allowing him to pass the board. As his driver calls after him, Thomas continues on over the unsafe rails which collapse and leave him teetering into a chasm.
Thomas realizes how silly he is by passing the board. Then the Fat Controller arrives, having seen everything. After telling Thomas off for his naughtiness, he begins to think about how to get Thomas out of the mine. As a crane would be too heavy for the ground to support, the Fat Controller decides to call Gordon to pull Thomas out. Thomas feels uneasy about this, feeling that he would rather not meet Gordon at the moment.
After being fitted with a winch on his front and being told about what happened, Gordon heads to the rescue unable to stop himself from laughing at the situation. Arriving at the mine, Gordon promises to get Thomas out as soon as possible. Strong cables are fastened between the two engines and after a lot of hard work and pulling, Gordon is able to finally get Thomas out of the mine.
Thomas apologises for his earlier cheekiness, but Gordon shrugs it off telling Thomas he actually thought his joke was funny. Now both engines are in disgrace, so Thomas and Gordon agree to form an alliance and help each other in future. With that, the two engines are coupled together and head back to the shed.
- When Thomas shunts Annie and Clarabel, his eyes look wonky and Annie and Clarabel are missing their names.